When succinic acid or the like is produced by fermentation, anaerobic bacteria such as Anaerobiospirillum or Actinobacillus are generally used (U.S. Pat. Nos. 5,143,834 and 5,504,004, and International Journal of Systematic Bacteriology (1999), 49, 207-216). When anaerobic bacteria are used, the yield of the products is high. However, since many nutrients are required for the growth of the bacteria, it is necessary to add a large amount of organic nitrogen source such as CSL (corn steep liquor) to a medium. Such addition of a large amount of organic nitrogen source causes not only an increase in the cost of the medium, but also an increase in the cost of purification of products when the products are taken out. Thus, it is not economical.
A method is known which comprises: culturing aerobic bacteria under aerobic conditions to allow cell to grow; collecting and washing the cell; and producing organic acids from static cell without aerating oxygen (JP Patent Publication (Kokai) No. 11-113588 A (1999)). In this case, only a small amount of organic nitrogen may be added to allow cell to grow, and the cell can sufficiently grow in a simple medium. Thus, this method is economical. However, the production amount of organic acid of interest and the production rate per cell are still insufficient. Therefore, it is desired that a more excellent method is established.
In addition, another method is known which involves a continuous culture in which bacteria are repeatedly cultured to produce L-glutamic acid or L-asparatic acid (JP Patent Publication (Kokai) Nos. 62-48394 A (1987) and 5-260985 A (1993)). However, to date, there have been no reports regarding a method for producing succinic acid by repeatedly culturing bacteria such as coryneform bacteria, Bacillus bacteria, or Rhizobium bacteria, particularly under anaerobic conditions.